1. Field of the Invention
The present invention relates to a charcoal canister for use in a fuel purge system of an internal combustion engine.
2. Description of the Related Art
In a conventional charcoal canister, a fuel vapor inlet pipe and a purge pipe extend outwardly from one end of a housing of the charcoal canister, and an outside air inlet pipe extends outwardly from the other end of the housing. This arrangement wherein the pipes extend from both ends of the housing causes problems in that the pipe fitting work is complicated.
As a solution to this problem, the fuel vapor inlet pipe, the purge pipe, and the outside air inlet pipe are extended outwardly from only one end of the housing, and therefore, the pipe fitting work can be easily carried out.
FIG. 6 shows a conventional charcoal canister (for example, as disclosed by Japanese Unexamined Utility Model Publication No. 54-58513), wherein a space 80 is formed at the bottom of the housing 1 of the charcoal canister, and a first activated carbon layer 82 and a second activated carbon layer 83 are defined on the space 80 by a dividing plate 81 extending longitudinally therefrom. A purge pipe 21 connected to the first activated carbon layer 82, an outside air inlet pipe 19 connected to the second activated carbon layer 83, and a fuel vapor inlet pipe 20 connected to the space 80 are extended outwardly from the top wall of the housing 1.
In this charcoal canister, however, when a fuel purge is carried out (gas flows through the outside air inlet pipe 19, the second activated carbon layer 83, the space 80, the first activated carbon layer 82, and the purge pipe 21, in this order), the flow area is equal to a section area A.sub.1 or A.sub.2 of the first activated carbon layer 82 or the second activated carbon layer 83, i.e., about a half of the section area A of the housing 1, and an effective length of the activated carbon layer is equal to twice the length L of the housing 1. Therefore a problem occurs in that pressure loss in the charcoal canister is increased. Also, an effective area in which air and fuel vapor come in contact with the activated carbon is equal to a half of the section area A of the housing 1, and therefore a problem occurs in that a reaction velocity in the activated carbon is reduced.